is it possible to fund clearance yourslef?
I think not. You must be sponsored by your job or the job that is hiring you.
Depends.. I think it can range from $5,000 + depending on the level of clearance.
im also unsure of how the security clearance process works, is it a worldwide thing or within national company?
As far as I know the clearance provided in the US is worldwide if you are going to be working for a US company.
what things go against people for security clearance?
Drugs, Theft, Credit history, Psychological background, Citizenship, etc...
im located within the UK and have previously been police cautioned a few years ago, would this stop me getting security cleared?
policed cautioned? Exactly what do you mean?
and is there any time limit for this staying on your record?
For a Top Secret clearance, the background check will go back 10 years or from the time you were 16years old. Whatever comes first.
what other factors come into this?
Family members that are from different countries could be a bad thing.
is there any way of cleaning your record in the same way it is possible to clean your credit record?
As far as I know you can not.
Sorry if I am not very detailed